ENTITY barrel_shift IS
  PORT (v : IN BIT_VECTOR(3 DOWNTO 0);
          d1, d0    : IN BIT;
          s : OUT BIT_VECTOR(3 DOWNTO 0));
END barrel_shift;

ARCHITECTURE teste OF barrel_shift IS
    SIGNAL sel: BIT_VECTOR(1 DOWNTO 0);
BEGIN
    sel <= d1 & d0;
    abc: PROCESS (sel, v)
    BEGIN
        IF sel = "00" THEN
          s <= v;
        ELSIF sel = "01" THEN
          s <= v rol 1;
        ELSIF sel = "10" THEN
          s <= v rol 2;
        ELSIF sel = "11" THEN
          s <= v rol 3;
        END IF;
    END PROCESS abc;
END teste;